Multilayer structure comprising a material covered with a copolymer having polyamide blocks and hydrophilic blocks

ABSTRACT

The present invention relates to a multilayer structure comprising a material covered with a copolymer having polyamide blocks and hydrophilic blocks where the copolymer has a melting point of less than 135° C.

The present invention relates to a multilayer structure comprising amaterial covered with a copolymer having polyamide blocks andhydrophilic blocks. It is, for example, a nonwoven coated withcopolymers having polyamide blocks and hydrophilic blocks.

These copolymers having polyamide blocks and hydrophilic blocks have amelting point of less than 135° C. and are very fluid in the melt. Theyconsist, for example, of blocks of carboxylic-acid-terminatedlauryllactam oligomers which are then condensed with a polyether diolsuch as polyethylene glycol. The Applicant has discovered that nonwovenscould be coated with these copolymers in order to obtain animpermeable-breathable material, i.e. one which is a barrier to liquidwater but which is permeable to water vapour.

The prior art EP 688826 has described impermeable-breathable filmsessentially consisting of copolymers having polyamide blocks andpolyether blocks which could be hot laminated directly to nonwovens inorder to obtain adhesion. These films may also be adhesively bonded tononwovens or any other substrate. The adhesive is placed in spots, or instripes in order not to impair the breathability. It has now beendiscovered that it is much simpler to cover the nonwoven with copolymershaving polyamide blocks and hydrophilic blocks in the melt.

After cooling, a material is obtained which has the same properties asthat of the prior art, that is to say of the impermeable-breathable filmlaminated or adhesively bonded to the nonwoven.

An advantage of the structure of the invention is the simplicity ofmanufacture compared with the hot-laminated or adhesively bonded film.Another advantage of the invention is the stability of this structure ina wet environment, while a film hot-laminated or adhesively bonded to anonwoven has a tendency to separate from the nonwoven if the adhesivebonding or the laminating has not been carried out carefully.

The material may be based on cellulose, such as paper, board, a nonwovenconsisting of cellulose fibres or a nonwoven based on polyolefin fibres.

The material may be a woven or a nonwoven.

The woven may be any woven used in the textile industry, particularlyfor clothing, for example cotton, polyamide or polyester. The nonwovenis generally based on fibres of a homopolymer or copolymer polyolefin,such as, for example, polyethylene, polypropylene or ethylene-alkyl(meth)acrylate copolymers .

The copolymers having polyamide blocks and hydrophilic blocks have amelting point of less than 135° C. and Preferably between 90 and 135° C.They are melt-deposited on the material and then, by cooling, thestructure of the invention is obtained. The melting point is determinedby DSC, (Differential Scanning Calorimetry). They may be deposited onthe material by extrusion.

The fluidity of the copolymers must be sufficient to be able, in themelt, to easily cover the material and form a structure which does notdelaminate.

Advantageously, the inherent viscosity of the copolymers in solution isbetween 0.8 and 1.75. This relative viscosity is measured as a 0.5%solution in metacresol using an Ostwald viscometer.

The hydrophilic blocks are defined as products that can absorb at least50% of their weight in equilibrium with liquid water.

Advantageously, these are polyethers having a sufficient proportion ofPEG units —(C₂H₄—O)— in order to make them hydrophilic.

The polymers having polyamide blocks and Polyether blocks result fromthe copolycondensation of polyamide blocks having reactive end groupswith polyether blocks having reactive end groups, such as, inter alia:

1) Polyamide blocks having diamine chain ends with Polyoxyalkyleneblocks having dicarboxylic chain ends;

2) Polyamide blocks having dicarboxylic chain ends with Polyoxyalkyleneblocks having diamine chain ends, obtained by cyanoethylation andhydrogenation of aliphatic dihydroxylated alpha,omega-polyoxyalkyleneblocks, called polyether diols;

3) Polyamide blocks having dicarboxylic chain ends with polyether diols,the products obtained being, in this special case, Polyetheresteramides.

The copolymers ofthe present invention are those advantageouslydescribed in point 3).

The polyamide blocks having dicarboxylic chain ends derive, for example,from the condensation of alpha,omega-aminocarboxylic acids of lactams orof dicarboxylic acids with diamines in the presence of a chain-limitingdicarboxylic acid.

According to a first preferred embodiment of the invention, thepolyamide blocks result, for example, from the condensation of one ormore alpha,omega-aminocarboxylic acids and/or of one or more lactamshaving from 6 to 12 carbon atoms in the presence of a dicarboxylic acidhaving from 6 to 12 carbon atoms and have a low mass, i.e. an {overscore(M)}_(n) of 400 to 1000. By way of example, of an alpha,omega-aminocarboxylic acid, mention may be made of aminoundecanoic andaminododecanoic acid. By way of example of a dicarboxylic acid, mentionmay be made of adipic acid, sebacic acid and dodecanedioic acidHOOC—(CH₂)₁₀—COOH.

By way of example of a lactam, mention may be made of caprolactam andlauryllactam.

Caprolactam should be avoided unless the polyamide is purified of thecaprolactam monomer which remains dissolved in it.

Polyamide blocks obtained by the condensation of lauryllactam in thepresence of adipic acid or of dodecanedioic acid and a mass {overscore(M)}n of 750 have a melting point of 127-130° C.

According to a second preferred embodiment of the invention, thepolyamide blocks result from the condensation of at least onealpha,omega-aminocarboxylic acid (or a lactam), at least one diamine andat least one dicarboxylic acid. The alpha,omega-aminocarboxylic acid,the lactam and the dicarboxylic acid may be chosen from those mentionedabove.

The diamine may be an aliphatic diamine having from 6 to 12 carbonatoms, it may be an aryl diamine.

By way of examples, mention may made of hexamethylenediamine,piperazine, isophorone diamine (IPD), methyl pentamethylenediamine(MPDM), bis(aminocyclohexyl)methane (BACM),bis(3-methyl-4-aminocyclohexyl)methane (BMACM).

The various constituents of the polyamide block and their proportion arechosen in order to obtain a melting point of less than 135° C. andadvantageously of between 90 and 135° C.

Caprolactam should be avoided unless the polyamide is purified of thecaprolactam which remains dissolved in it.

By way of examples of polyamide blocks, mention may be made of thefollowing:

a) 6,6/Pip. 10/12

 in which

6,6 denotes hexamethyleneadipamide (hexamethylenediamine condensed withadipic acid) units;

Pip. 10 denotes units resulting from the condensation of piperazine withsebacic acid;

12 denotes units resulting from the condensation of lauryllactam.

The proportions by weight are respectively:

25 to 35/20 to 30/20 to 30, the total being 80 and advantageously 30 to35/22 to 27/22 to 27, the total being 80.

For example, the proportions 32/24/24 result in a melting point of 122to 137° C.

b) 6,6/6,10/11/12

 in which

6,6 denotes hexamethylenediamine condensed with adipic acid;

6,10 denotes hexamethylenediamine condensed with sebacic acid;

11 denotes units resulting from the condensation of aminoundecanoicacid;

12 denotes units resulting from the condensation of lauryllactam.

The proportions by weight are respectively:

10 to 20/15 to 25/10 to 20/15 to 25, the total being 70, andadvantageously:

12 to 16/18 to 25/12 to 16/18 to 25, the total being 70.

For example, the proportions 14/21/14/21/result in a melting point of119 to 131° C.

The hydrophilic blocks are polyether diols having a proportion of—(C₂H₄—O)— units sufficient to make them hydrophilic and advantageouslyat least 50% by weight.

The polyether blocks may include units other than those of ethyleneoxide, for example propylene oxide units or (—(CH₂)₄—O)— units.

The blocks are advantageously polyethylene glycol (PEG) blocks.

The copolymers of the invention may also include PPG (polypropyleneglycol) blocks or PTMG (polytetramethylene glycol) blocks provided thatthere is a sufficient proportion of PEG blocks or blocks having aproportion of —(C₂H₄—O)— units sufficient for the copolymers of theinvention, once converted into film or coated onto a nonwoven, areimpermeable-breathable. Advantageously, the impermeable-breathablecharacter measured by the water-vapour permeability according to theASTM E 96 BW standard is greater than 1000 and preferably between 2000and 15,000 g/m²/24 h.

Advantageously, the polyether blocks are PEG blocks with a mass{overscore (M)}n of 100 to 6000 and preferably of 500 to 3000.

The amount of polyether blocks represents 10 to 40% by weight of thecopolymer of the invention.

Particularly advantageous copolymers are:

those having polyamide-12 (polylauryllactam) blocks with a mass{overscore (M)}n of 750 and PEG blocks with an {overscore (M)}n of 1500or 1000;

those having 6,6/Pip. 10/12 polyamide blocks described above in a) andPEG blocks with a mass {overscore (M)}n of 600;

those having 6,6/6,10/11/12 polyamide blocks described above at b) andPEG blocks with a {overscore (M)}n of 600.

The copolymers of the invention may be prepared by any means allowingthe polyamide blocks and the polyether blocks to be linked together. Inpractice, essentially two processes are used, one being called atwo-step process and the other a one-step process.

The two-step process firstly consists in preparing the polyamide blockshaving carboxylic end groups by condensation of polyamide precursors inthe presence of a chain-limiting dicarboxylic acid and then, in a secondstep, in adding the polyether and a catalyst. If the polyamideprecursors are only lactams or alpha,omega-aminocarboxylic acids, adicarboxylic acid is added. If the precursors already comprise adicarboxylic acid, this is used in excess with respect to thestoichiometry of the diamines. The reaction usually takes place between180 and 300° C., preferably 200 to 260° C., the pressure in the reactorstabilizes between 5 and 30 bar and maintained for approximately 2hours. The pressure is slowly reduced, by venting the reactor, and thenthe excess water is distilled off, for example for one hour or two.

Having prepared the polyamide with carboxylic acid end groups, thepolyether and a catalyst are then added. The polyether may be added inone or more goes, as may the catalyst. According to one advantageousembodiment, the polyether, is firstly added, the reaction of the OH endgroups of the polyether with the COOH end groups of the polyamide startswith the formation of ester linkages and the elimination of water; thewater of the reaction mixture is eliminated as far as possible bydistillation and then the catalyst is introduced in order to completethe linking of the polyamide blocks to the polyether blocks. This secondstep is carried out with stirring, preferably under a vacuum of at least5 mmHg (650 Pa) at a temperature such that the reactants and thecopolymers obtained are in the melt. By way of example, this temperaturemay be between 100 and 400° C. and usually between 200 and 300° C. Thereaction is monitored by measuring the torsional couple exerted by themolten polymer on the stirrer or by measuring the electric powerconsumed by the stirrer. The end of the reaction is determined by thevalue of the couple or the target power. The catalyst is defined asbeing any product allowing the polyamide blocks to be linked to thepolyether blocks by esterification. The catalyst is advantageously aderivative of a metal (M) chosen from the group formed by titanium,zirconium and hafnium.

By way of example of a derivative, mention may be made of tetraalkoxideswhich satisfy the general formula M(OR)₄, in which M representstitanium, zirconium or hafnium and the Rs, which are identical ordifferent, denote linear or branched alkyl radicals having from 1 to 24carbon atoms.

The C₁ to C₂₄ alkyl radicals from among which the radicals R of thetetraalkoxides used as catalysts in the process according to theinvention are chosen are, for example, such as methyl, ethyl, propyl,isopropyl, butyl, ethylhexyl, decyl, dodecyl and hexadodecyl. Thepreferred catalysts are the tetraalkoxides for which the radicals R,which are identical or different, are C₁ to C₈ alkyl radicals. Examplesof such catalysts are, in particular, Z_(r) (OC₂H₅)₄, Zr (O-isoC₃H₇)₄,Zr(OC₄H₉)₄, Zr(OC₅H₁₁)₄, Zr(OC₆H₁₃)₄, Hf(OC₂H₅)₄, Hf(OC₄H₉)₄ andHf(O-isoC₃H₇)₄.

The catalyst used in this process according to the invention may consistonly of one or more of the tetraalkoxides of formula M(OR)₄ definedabove. It may also be formed by the combination of one or more of thesetetraalkoxides with one or more alkali or alkaline-earth metal alkoxidesof formula (R₁O)_(p)Y in which R₁ denotes a hydrocarbon residue,advantageously a C₁ to C₂₄, and preferably C₁ to C₈, alkyl residue, Yrepresents an alkali or alkaline-earth metal and p is the valency of Y.The amounts of alkali or alkaline-earth metal alkoxide and of zirconiumor hafnium tetraalkoxides which are combined in order to form the mixedcatalyst may vary over wide limits. However, it is preferred to useamounts of alkoxide and of tetraalkoxides such that the molar proportionof alkoxide is approximately equal to the molar proportion oftetraalkoxide.

The proportion of catalyst by weight, that is to say of thetetraalkoxide or tetraalkoxides when the catalyst does not contain analkali or alkaline-earth metal alkoxide, or else of the combination ofthe tetraalkoxide or tetraalkoxides and the alkali or alkaline-earthmetal alkoxide or alkoxides, when the catalyst is formed by thecombination of these two types of compounds, advantageously varies from0.01 to 5% of the weight of the mixture of the dicarboxylic polyamidewith the polyoxyalkylene glycol and preferably lies between 0.05 and 2%of this weight.

By way of example of other derivatives, mention may also be made ofsalts of the metal (M), particularly the salts of (M) and of an organicacid and the complex salts between the oxide of (M) and/or the hydroxideof (M) and an organic acid. Advantageously, the organic acid may beformic acid, acetic acid, propionic acid, butyric acid, valeric acid,caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid,stearic acid, oleic acid, linolic acid, linolenic acid,cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, salicylicacid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipicacid, maleic acid, fumaric acid, phthalic acid and crotonic acid. Aceticand propionic acids are particularly preferred. Advantageously, M iszirconium. These salts may be called zirconyl salts. The Applicantbelieves, without being tied to this explanation, that these salts ofzirconium and an organic acid or the complex salts mentioned aboverelease ZrO⁺⁺ during the process. The product sold under the namezirconyl acetate is used. The amount to be used is the same as for theM(OR)₄ derivatives.

This process and these catalysts are described in Patents U.S. Pat No.4,332,920, U.S. Pat. No. 4,230,838, U.S. Pat. No. 4,331,786, U.S. Pat.No. 4,252,920, JP 07145368A, JP 06287547A and EP 613919.

The present invention also relates to this two-step process forpreparing copolymers having polyamide blocks and hydrophilic blocks witha melting point of less than 135° C. and which were described above inthe multilayer structure, in which process the catalyst is a salt of themetal (M) chosen from the group of salts of (M) and of an organic acidand of complex salts between the oxide of (M) and/or the hydroxide of(M) and an organic acid. Advantageously (M) is zirconium. Preferably,the catalyst is zirconyl acetate.

With regard to the one-step process, all the reactants used in thetwo-step process, i.e. the polyamide precursors, the chain-limitingdicarboxylic acid, the polyether and the catalyst are mixed. These arethe same reactants and the same catalyst as in the two-step processdescribed above. If the polyamide precursors are only lactams, it isadvantageous to add a little water.

The copolymer has essentially the same polyether blocks and the samepolyamide blocks, but also a small portion of the various reactants thathave reacted in a random fashion and are distributed randomly along thepolymer chain.

The reactor is closed and heated, with stirring, as in the first step ofthe two-step process described above. The pressure stabilizes between 5and 30 bar. When it no longer changes, the reactor is put under areduced pressure, while maintaining vigorous stirring of the moltenreactants. The reaction is monitored as before, in the case of thetwo-step process.

The catalyst used in the one-step process is preferably a salt of themetal (M) and of an organic acid, or a complex salt between the oxide of(M) and/or the hydroxide of (M) and an organic acid.

The present invention also relates to this one-step process forpreparing copolymers having polyamide blocks and hydrophilic blocks witha melting point of less than 135° C. and which are described above inthe multilayer structure, in which process the catalyst is a salt of themetal (M) chosen from the group of salts of (M) and of an organic acidand of complex salts between the oxide of (M) and/or the hydroxide of(M) and an organic acid. Advantageously (M) is zirconium. Preferably,the catalyst is zirconyl acetate.

The present invention also relates to certain copolymers havingpolyamide blocks and hydrophilic blocks of the multilayer structuredescribed above and more particularly those which do not contain unitscoming from caprolactam or from the corresponding amino acid.

U.S. Pat. No. 5,489,667 has described copolymers having polyamide blocks(i), produced from caprolactam and aminoundecanoic acid and from thereaction of hexamethylenediamine on adipic acid, and PEG blocks (ii).These copolymers having a melting point of between 90 and 130° C. areuseful as HMA-type adhesives (or hot-melt adhesives), that is to saythey are deposited in the melt on the surfaces to be bonded and then theadhesion is obtained when they return to the solid state by cooling.

The Applicant has found that if caprolactam (or the corresponding aminoacid) is used for preparing the polyamide blocks in the copolymers ofthe structures of the invention, it is very difficult to eliminate thecaprolactam (or the corresponding amino acid) that has not polymerizedin the polyamide block. When the copolymer is melted in order to coverthe material and form the multilayer structure of the invention,caprolactam vapour, which has an unpleasant smell, is released. TheApplicant has discovered that although the prior art always teaches theuse of caprolactam (or of the corresponding amino acid) for thesecopolymers, it is not in fact necessary to use it.

The present invention relates to the copolymers having polyamide blocksand polyether blocks resulting from the chain-linkage of polyamideblocks having carboxylic end groups to polyether diols, these copolymershave a melting point between 90 and 135° C. and the polyamide blocksresult from the condensation of one or more alpha,omega-aminocarboxylicacids and/or of one or more lactams having from 10 to 12 carbon atoms inthe presence of a dicarboxylic acid having from 6 to 12 carbon atoms.These polyamide blocks have a low mass {overscore (M)}n, i.e. between400 and 1000.

Advantageously, the polyamide blocks result from the condensation of apolyamide precursor chosen from aminoundecanoic acid, aminododecanoicacid and lauryllactam in the presence of adipic acid, azelaic acid,sebacic acid or dodecanedioic acid.

The present invention also relates to the copolymers having polyamideblocks and polyether blocks resulting from the chain-linkage ofpolyamide blocks having carboxylic end groups to polyether diols; thesecopolymers have a melting point of between 90 and 135° C. and thepolyamide blocks result from the condensation:

of one or more diamines with one or more dicarboxylic acids each havingfrom 6 to 12 carbon atoms;

of at least one lactam and/or one alpha,omega-aminocarboxylic acidhaving from 10 to 12 carbon atoms;

at least one of the dicarboxylic acids being in excess.

In these copolymers having polyamide blocks and polyether blocks, thelactam and/or the alpha,omega-aminocarboxylic acid is advantageouslychosen from aminoundecanoic acid, aminododecanoic acid and lauryllactam.

Mention may be made, for example, of the blocks a) and b) mentionedabove, namely:

a) 6,6/Pip. 10/12

b) 6,6/6,10/11/12 and the blocks 6,6/12/11/6,9/6,12, in which:

6,9 denotes the condensation of hexamethylenediamine with azelaic acid;

6,12 denotes the condensation of hexamethylenediamine with dodecanedioicacid.

These copolymers result from the chain-linkage of polyamide blockshaving carboxylic end groups to polyether diol blocks.

The polyether diol blocks are those described above, preferably they arepolyethylene glycol (PEG) blocks.

These polymers deposited on the material and forming part of themultilayer structure of the invention are also useful as adhesives.

It is not always desirable, or possible, to cover materials with thecopolymers of the invention in the melt. For example, with theseadhesives, breathing films may be adhesively bonded to leather and tocotton or polyester wovens. These are adhesives of the HMA type (orhot-melt adhesives), that is to say they are deposited in the moltenstate on the surfaces to be adhesively bonded and then the adhesion isobtained when they return to the solid state by cooling. Thus, thepresence of the adhesive does not produce the breathability since it isitself impermeable-breathable by virtue of the PEG blocks. If, however,a breathable film is adhesively bonded to a nonwoven using anon-breathable adhesive, the breathability of the assembly is greatlyreduced, depending on the density of the spots of adhesive.

The present invention also relates to the hot-melt adhesives consistingof the novel copolymers not having caprolactam in the polyamide blocks.

EXAMPLE 1

Introduced into a 6-litre reactor are 661 g of dicarboxylic polyamide 12having an average molecular mass of 750 g/mol, prepared beforehand bythe polycondensation of lauryllactam in the presence of adipic acid.Next, 838 g of dihydroxylated polyoxyethylene (PEG) having a molecularmass of 1000 g/mol and then 1.5 g of Zr(OC₄H₉)₄ are added.

The mixture thus formed is put under an inert atmosphere and heateduntil the temperature reaches 240° C.

The reactor is then put under reduced pressure, while maintainingvigorous stirring as soon as the reactants melt. The reaction iscontinued at 240° C. under 1 torr (130 Pa) for a period of 1 hour.

The product obtained has an inherent viscosity of 1.39 dl/g. It has acrystalline melting point at 133° C. in differential thermal analysis.

EXAMPLE 2

Introduced into a 6-litre reactor are 451 g of 12-aminododecanoic acid,102 g of adipic acid and 1000 g of dihydroxylated polyoxyethylene havingan average molecular mass of 1500 g/mol.

The mixture thus formed is put under an inert atmosphere and heateduntil the temperature; reaches 240° C., while maintaining vigorousstirring, as, soon as the reactants melt. The mixture is left to reactfor 2 hours and then the water created is distilled off. Next, 4.5 g ofZr(OC₄H₉)₄ in 7.5 g of CH₂Cl₂ are introduced and the reactor is putunder reduced pressure, maintaining stirring.

The reaction is continued at 220° C. under 1 torr (130 Pa) for a periodof 2 hours.

The product obtained has an inherent viscosity of 1.41 dl/g. It has acrystalline melting peak at 135° C. in differential thermal analysis.

EXAMPLE 3

Introduced into a 6-litre reactor are 391 g of 12-lactam, 158.84 g ofdodecanoic acid, 35 g of water, 1500 g of dihydroxylated polyoxyethylenehaving an average molecular mass of 1500 g/mol and 7.8 ml of a zirconylacetate solution in water/acetic acid (0.625% total loading of zirconylacetate).

The mixture thus formed is put under an inert atmosphere and heateduntil the temperature reaches 270° C., while maintaining vigorousstirring, as soon as the reactants melt, for 3 hours, after which thepressure, which is then 30 bar, is then released. When atmosphericpressure is reached, the reactor is put under a reduced pressure of 1torr (130 Pa). The reaction is continued for a period of 2 hours.

The product obtained has an inherent viscosity of 1.27 dl/g. It has acrystalline melting peak at 135° C. in differential thermal analysis.

EXAMPLE 4

Introduced into a 6-litre reactor are 391 g of 12-lactam, 179 g ofdodecanoic acid, 35 g of water, 1500 g of dihydroxylated polyoxyethylenehaving an average molecular mass of 1500 g/mol and 9.4 ml of zirconylacetate solution in water/acetic acid (0.625% total loading of zirconylacetate).

The mixture thus formed is put under an inert atmosphere and heateduntil the temperature reaches 270° C., while maintaining vigorousstirring, as soon as the reactants melt, for 3 hours, after which thepressure, which is then 30 bar, is then released. When atmosphericpressure is reached, the reactor is put under a reduced pressure of 1torr (130 Pa). The reaction is continued for a period of 2 hours.

The product obtained has an inherent viscosity of 1.27 dl/g. It has acrystalline melting peak at 102° C. in differential thermal analysis.

EXAMPLE 5

Preparation of the 6,6/6,10/12/PEG.600 copolymer in the proportions14/14/42/30.

The following monomers are introduced into an autoclave which is fittedwith a stirrer: 16,800 g of lauryllactam, 3557 g of sebacic acid (C10),5408 g of adipic acid and 6188 g of hexamethylenediamine (in the form ofa 73.1% solution in water).

The mixture thus formed is put under an inert atmosphere and heateduntil the temperature reaches 290° C., while maintaining vigorousstirring, as soon as the reactants melt. A temperature of 290° C. and apressure of 25 bar are maintained for 2 hours (precondensation). Next,the pressure is slowly (1.25 h) reduced from 25 bar to atmosphericpressure and the temperature from 290 to 245° C. A fine dispersion of9711 g of dihydroxylated polyoxyethylene (M_(n)=600) and 70 g of azirconyl acetate solution in water/acetic acid (0.625% total loading ofthe zirconyl acetate; pH_(solution)=3.0-3.5) are now introduced.

The mixture obtained is put under reduced pressure of ca. 30 mbar. Thereaction is continued for a period of 3 hours. The product is extrudedinto a water bath and granulated. The product obtained has an inherentviscosity of 1.12 dl/g; melting point (determined optically): 120-130°C.

EXAMPLE 6

The permeability of a 40 μm thick film of composition 6/11/6,12/PEG inproportions 21/21/18/40 is 12,000 g/m²/24 h according to ASTM E 96 BW.

What is claimed is:
 1. Multilayer structure comprising a materialwherein the material is paper, board, a nonwoven comprising cellulosefibres, a nonwoven comprising polyolefin fibres or a woven chosen fromcotton, polyamide or polyester covered with a copolymer having polyamideblocks with the proviso that the polyamide blocks are not condensed fromcaprolactam and hydrophilic blocks wherein the hydrophilic blocks of thecopolymer are polyethers having at least 50% by weight of —(C₂H₄—O)—units, the copolymer having a melting point of less than 135° C.;wherein the structure is a barrier to water and permeable to watervapor.
 2. Structure claim 1, in which the amount of polyether blocks ofthe copolymer represents 10 to 40% by weight of the copolymer. 3.Structure according claim 1, in which the polyamide blocks of thecopolymer result from the condensation of one or morealpha,omega-aminocarboxylic acids and/or of one or more lactams havingfrom 6 to 12 carbon atoms in the presence of a dicarboxylic acid havingfrom 6 to 12 carbon atoms, the polyamide blocks having a mass {overscore(M)}n of 400 to
 1000. 4. Structure according to claim 1, in which thepolyamide blocks of the copolymer result from the condensation of atleast one alpha,omega-aminocarboxylic acid or of a lactam, at least onediamine and at least one dicarboxylic acid.
 5. Process for preparing astructure according to claim 3, in which (i) in a first step, thepolyamide blocks are prepared by condensation of polyamide precursors inthe presence of a chain-limiting dicarboxylic acid and then (ii), in asecond step, the polyether and a catalyst, which is a salt of metal (M)chosen from the group of salts of (M) and of an organic acid and ofcomplex salts between the oxide of (M) and/or the hydroxide of (M) andan organic acid, are added.
 6. Process for preparing a structureaccording to claim 1, in which the polyamide precursors, achain-limiting dicarboxylic acid, the polyether and a catalyst, which isa salt of metal (M) chosen from the group of salts of (M) and of anorganic acid and of complex salts between the oxide of (M) and/or thehydroxide of (M) and an organic, are mixed.
 7. Process according toclaim 5, in which (M) is chosen from titanium, zirconium and hafnium. 8.Process according to claim 7, in which (M) is zirconium.
 9. Processaccording to claim 5, in which the catalyst is zirconyl acetate.
 10. Astructure according to claim 1, wherein the copolymer has a meltingpoint of 90-135° C.
 11. A process for preparing a structure according toclaim 4, wherein (i) the polyamide blocks are prepared by condensationof polyamide precursors in the presence of a chain-limiting dicarboxylicacid and then (ii) the polyether and a catalyst, which is a salt ofmetal (M) chosen from the group of salts of (M) and of an organic acidand of complex salts between the oxide of (M) and/or the hydroxide of(M) and an organic acid, are added.
 12. A process for preparing astructure according to claim 4, wherein the polyamnide precursors, achain-limiting dicarboxylic acid, the polyether and a catalyst, which isa salt of metal (M) chosen from the group of salts of (M) and of anorganic acid and of complex salts between the oxide of (M) and/or thehydroxide of (M) and an organic, are mixed.
 13. Process according toclaim 11, in which (M) is chosen from titanium, zirconium and hafnium.14. Process according to claim 13, in which (M) is zirconium. 15.Process according to claim 11, in which the catalyst is zirconylacetate.
 16. Structure according to claim 4 wherein the lactam or thealpha, omega-aminocarboxylic acid is chosen from aminoundecanoic acid,aminododecanoic acid and lauryllactam.
 17. A copolymer having polyamideblocks and polyether blocks resulting from the chain-linkage ofpolyamide blocks having carboxylic acid end groups to polyether diolswherein the polyether diols are polyethylene glycol, having a meltingpoint of between 90 and 135° C. in which the polyamide blocks resultfrom the condensation of one or more alpha, omega-aminocarboxylic acidsand/or one or more lactams having from 10 to 12 carbon atoms in thepresence of a dicarboxylic acid having from 6 to 12 carbon atoms withthe proviso that the polyamide blocks are not condensed from caprolactamor the corresponding amino acid, and in which the mass M_(n) of thepolyamide blocks is between 400 and
 1000. 18. A copolymer according toclaim 17, in which the lactam and/or the alpha, omega-aminocarboxylicacid having from 10 to 12 carbon atoms is chosen from aminoundecanoicacid, aminododecanoic acid and lauryllactam.
 19. A copolymer accordingto claim 18, having 6,6/Pip.10/12 polyamide blocks, in which: 6,6denotes units resulting from the condensation of hexamethylenediaminewith adipic acid; Pip. 10 denotes units resulting from the condensationof piperazine with sebacic acid; 12 denotes units resulting from thecondensation of lauryllactam.
 20. A copolymer according to claim 18,having 6,6/6,12/11/12 polyamide blocks in which: 6,6 denotes unitsresulting from the condensation of hexamethylenediamine with adipicacid; 6,12 denotes units resulting from the condensation ofhexamethylenediamine with dodecanedioic acid; 11 denotes units resultingfrom the condensation of aminoundecanoic acid; 12 denotes unitsresulting from the condensation of lauryllactam.
 21. A copolymer havingpolyamide blocks and polyether blocks resulting from the chain-linkageof polyamide blocks having carboxylic end groups to polyether diolswherein the polyether diols are polyethylene glycol, these copolymershaving a melting point of between 90 and 135° C. and in which thepolyamide blocks result from the condensation: of one or more diamineswith one or more dicarboxylic acids each having from 6 to 12 carbonatoms; of at least one lactam and/or one alpha, omega-aminocarboxylicacid having from 10 to 12 carbon atoms; at least one of the dicarboxylicacids being in excess, with the proviso that the polyamide blocks arenot condensed from caprolactam.
 22. A copolymer according to claim 21,wherein the lactal and/or the alpha, omega-amnocarboxylic acid havingfrom 10 to 12 carbon atoms is chosen from aminoundecanoic acid,aminododecanoic acid and lauryllactam.
 23. Hot-melt adhesive comprisinga copolymer having polyamide blocks and polyether blocks resulting fromthe chain-linkage of polyamide blocks having carboxylic acid end groupsto polyether diols wherein the polyether diols are polyethylene glycol,having a melting point of between 90 and 135° C. in which the polyamideblocks result from the condensation of one or more alpha,omega-aminocarboxylic acids and/or one or more lactams having from 10 to12 carbon atoms in the presence of a dicarboxylic acid having from 6 to12 carbon atoms with the proviso that the polyamide blocks are notcondensed from caprolactam, and in which the mass M_(n) of thepolyamnide blocks is between 400 and
 1000. 24. Hot-melt adhesiveaccording to claim 23 wherein the lactam and/or the alpha,omega-aminocarboxylic acid having from 10 to 12 carbon atoms is chosenfrom aminoundecanoic acid, aminododecanoic acid and lauryllactam.